In December, 1992 Devane et at. reported the discovery of an endogenous molecule isolated from brain that displace a cannabinoid receptor probe and possessed biologic activity similar to 9- tetrahydrocannabinol. (9-THC) The endogenous ligan was determined to be arachidonylethanolamide and was named anadamide (AN). We have obtained AN from Prof. Mechoulam and also synthesized our own radiolabeled and non-radiolabeled compound. Our preliminary experiments show that AN has 9-THC-like activity in that it produces analgesia, decreases spontaneous locomotion and produces hypothermia, Its CNS action appears to be weaker and of shorter duration than that of 9-THC. Our in vitro experiments suggest that AN can be synthesized by brain from H-arachidonic acid and that when added to brain AN is metabolized to rachidonic acid (AA). Arachidonic acid metabolism in brain is known to produce oxygen radicals and compounds which modulated brain blood flow. Our preliminary studies show that AN alone has little effect on cerebral blood vessels but its presence enhances the arteriolar response to acetylcholine and bradykinin, two agents known to activate prostaglandin formation. Therefore AN appears to affect behaviors as well as regulation of brain blood flow. We wish to test 3 hypotheses using techniques currently in our laboratories. Our first hypothesis is that AN produces the same pharmacological and behavioral profiles as 9-THC in mice and rats, as well as exhibiting similar receptor binding characteristics. This hypothesis will be examined using the tail flick assay for analgesia, studies of locomotion, drug discrimination and cannabinoid receptor binding. Or second hypothesis is that AN is synthesized and metabolized by brain and that factors which are known to release AA or alter AA metabolism affect AN formation. This hypothesis will be tested using radiolabeled probes, HPLC, gas chromatography/mass spectrometry, brain slices and primary cultures of neurons and astrocytes. Our third hypothesis is that metabolism of AN produces free AA which in turn affects cerebral blood flow regulation. This hypothesis will be tested using the closed cranial window technique for observation of in vivo cerebral arteriolar reactivity. Whether anandamide is the only or most active endogenous ligand for the cannabinoid receptor is uncertain. However the report of Devane et al. and our own preliminary studies support the likely importance of this newly discovered, biologically active molecule and emphasize the need for its rigorous examination. Our aims are consistent with our long term goals of elucidating cannabinoid pharmacology and the brain synthesis and action of arachidonic acid metabolites.